1. Field of the Invention
This invention relates to packaging. More specifically, the invention relates to a multi-sided container or box made of corrugated paperboard. In particular, the invention relates to a corrugated paperboard tray for containing poultry products, wherein the tray is configured for manual set up and has an improved self locking feature for retaining the walls of the tray in erected position.
2. Prior Art
Various styles of containers, including paperboard boxes, are known in the prior art for containing a variety of products. Cut poultry pieces, for example, are frequently packed in a paperboard container, and sometimes the poultry pieces are packed with ice. These containers are generally referred to as poultry trays, and are usually made from a unitary blank of corrugated paperboard, which may be treated on one or both sides with wax or other material to impart rigidity and resistance to water degradation.
Conventional paperboard containers are configured for either machine set up or manual set up, and generally are either rectangular or octagonal in plan view, with four sides or eight sides, respectively. An example of a prior art eight sided container is disclosed in applicant's prior U.S. Pat. No. 5,752,648. The embodiment shown in FIGS. 1-3 of that patent is configured for manual set up, and has three overlapping end panels 18, 24 and 24, with notches 30 formed in the top edges of the two end panels 24, and a roll over flap 34 foldably joined to the top edge of end panel 18 by short narrow webs formed between transverse cuts or relief slits 37 extending in spaced relationship transversely across cut lines 36 and 38, and interrupting the cut lines. Pairs of short cuts or slits 39 are formed in the webs parallel to the cut lines 36 and 38, but spaced from one another on opposite sides of the cut lines a distance approximately equal to the combined thicknesses of the three overlapped end panels. The slits 39 promote bending or folding of the webs along fold lines extending through the slits.
To erect the container, the two end panels 24 are folded inwardly into overlapping registry with one another, and the end panel 18 is then folded into overlapping relationship with panels 24. The roll over flap 34 is then folded inwardly and downwardly over the upper edges of the panels 24, causing the webs to drop into notches 30, and the upwardly extending portions of panels 24 on opposite sides of the notches to project upwardly through the cuts formed by the cut lines 36 and 38. The relationship of the relief slits 37 and cut lines 36 and 38 causes a “heel” to be formed on the edge of the roll over flap, and this heel produces an over-center effect when the roll over flap is folded over the panels 24. The heel engages against the inner surface of the innermost end panel 24 to keep the roll over flap in its folded position, and thereby maintains the container in erected condition.
While the arrangement disclosed in U.S. Pat. No. 5,752,648 provides a simple and effective self locking system for holding the container in its erected condition, the thickness of the material of the webs causes them to take a slightly “rounded over” shape as they are pulled down into the notches 30, and they tend to exert a pull on the roll over flap in a direction to disengage it. Additionally, in order to insure that the webs and related components can be operatively engaged with one another, specific dimensional relationships are maintained between the distance from the bottoms of the notches to the bottom of their associated panels 24, and the distance which the relief slits 37 extend above the cut lines 36 and 38, i.e., the length of the relief slits is slightly exaggerated, contributing to a “loose” fit between the components of the self locking arrangement.
Accordingly, there is need for a self locking arrangement that provides a tight, secure fit between components, insuring that a container incorporating the arrangement reliably remains in its erected condition.